From patchwork Fri Feb 17 16:09:36 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miklos Szeredi X-Patchwork-Id: 9580321 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 01F61600F6 for ; Fri, 17 Feb 2017 16:10:02 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DF7982873D for ; Fri, 17 Feb 2017 16:10:01 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id D81C728739; Fri, 17 Feb 2017 16:10:01 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 748C22873D for ; Fri, 17 Feb 2017 16:10:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934739AbdBQQJ4 (ORCPT ); Fri, 17 Feb 2017 11:09:56 -0500 Received: from mail-wm0-f47.google.com ([74.125.82.47]:35004 "EHLO mail-wm0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934600AbdBQQJx (ORCPT ); Fri, 17 Feb 2017 11:09:53 -0500 Received: by mail-wm0-f47.google.com with SMTP id v186so19436195wmd.0 for ; Fri, 17 Feb 2017 08:09:52 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=CyUgP918V1eBwtnN46N9O3eIPuiwtgEL9IRIBc0wpxk=; b=cbPcpna+xfP+zglezgtKnTiApQ+aSV+6GgEeS9k4wsQ0S/nhIsNzOjEF9tTXnT2/N1 AUzEdGnV8E2WctfaxmtQQdx20YgztAjSilQTq77KepFlJWsTjQZe+4q2vWYVHneEhXc2 q+OTG05CJFI5wp+JNNWcRi/DB3Gmg1vgY4rOCFnIjJSHWfORAzeD+ne3kGSaUOTnvqYI tSkV5cu10VL+Rx6IiR4Qli+pKfq6XOUusoIvDUtnrlPRguNbzNQPc+kshfNDKCEmdP1m cJ8VU748scyfK1iudRWHw5lBGH5ck8xmpDEUcnlbd6G8I+am9J2jFzZBP0lHtiV60A5V xy8g== X-Gm-Message-State: AMke39kiCbCZLUGWP+J5QD/yRbtPYel3606oegTjOHhs1Fj8h+Jv6qY+zOqRGKLYHoaw7MeG X-Received: by 10.28.12.68 with SMTP id 65mr4503334wmm.100.1487347791824; Fri, 17 Feb 2017 08:09:51 -0800 (PST) Received: from veci.piliscsaba.szeredi.hu (pool-dsl-2c-0018.externet.hu. [217.173.44.24]) by smtp.gmail.com with ESMTPSA id h23sm4538793wrc.48.2017.02.17.08.09.50 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 17 Feb 2017 08:09:51 -0800 (PST) From: Miklos Szeredi To: Al Viro Cc: linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH 7/9] ovl: intercept mmap on overlay files Date: Fri, 17 Feb 2017 17:09:36 +0100 Message-Id: <1487347778-18596-8-git-send-email-mszeredi@redhat.com> X-Mailer: git-send-email 2.5.5 In-Reply-To: <1487347778-18596-1-git-send-email-mszeredi@redhat.com> References: <1487347778-18596-1-git-send-email-mszeredi@redhat.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP ... in order to handle the corner case when the file is copied up after being opened read-only and mapped shared. Can be verified with the following script: - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - - cd / rm -rf /tmp/ovl-rorw-test mkdir /tmp/ovl-rorw-test cd /tmp/ovl-rorw-test cat << EOF > rorw-map.c #include #include #include #include #include int main(int argc, char *argv[]) { int rofd, rwfd; int ret; char buf[4]; char *addr; rofd = open(argv[1], O_RDONLY); if (rofd == -1) err(1, "ro open"); addr = mmap(NULL, 4, PROT_READ, MAP_SHARED, rofd, 0); if (addr == MAP_FAILED) err(1, "ro mmap"); if (memcmp(addr, "bubu", 4) == 0) errx(1, "identical startup data"); rwfd = open(argv[1], O_WRONLY); if (rwfd == -1) err(1, "rw open"); ret = write(rwfd, "bubu", 4); if (ret == -1) err(1, "write"); if (ret < 4) errx(1, "short write"); if (memcmp(addr, "bubu", 4) != 0) errx(1, "bad mmap data"); ret = read(rofd, buf, 4); if (ret == -1) err(1, "read"); if (ret < 4) errx(1, "short read"); if (memcmp(buf, "bubu", 4) != 0) errx(1, "bad read data"); return 0; } EOF gcc -o rorw-map rorw-map.c mkdir -p mnt lower upper work echo baba > lower/foo mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work mnt ./rorw-map mnt/foo umount mnt - 8< - - - - - 8< - - - - - 8< - - - - - 8< - - - - No output means success, "rorw-map: bad mmap data" means failure. Signed-off-by: Miklos Szeredi --- fs/overlay_util.c | 19 +++++++++++++++++++ include/linux/fs.h | 3 +++ include/linux/overlay_util.h | 2 ++ mm/mmap.c | 3 +++ 4 files changed, 27 insertions(+) diff --git a/fs/overlay_util.c b/fs/overlay_util.c index 0daff19bad0b..063f8c5719d1 100644 --- a/fs/overlay_util.c +++ b/fs/overlay_util.c @@ -10,6 +10,7 @@ #include #include #include +#include #include "internal.h" static bool overlay_file_consistent(struct file *file) @@ -36,4 +37,22 @@ ssize_t overlay_read_iter(struct file *file, struct kiocb *kio, } EXPORT_SYMBOL(overlay_read_iter); +int overlay_mmap(struct file *file, struct vm_area_struct *vma) +{ + if (unlikely(!overlay_file_consistent(file))) { + file = filp_clone_open(file); + if (IS_ERR(file)) + return PTR_ERR(file); + + fput(vma->vm_file); + /* transfer ref: */ + vma->vm_file = file; + + if (!file->f_op->mmap) + return -ENODEV; + } + return file->f_op->mmap(file, vma); +} +EXPORT_SYMBOL(overlay_mmap); + #endif /* IS_ENABLED(CONFIG_OVERLAY_FS) */ diff --git a/include/linux/fs.h b/include/linux/fs.h index 4728c5178f3f..6e74b726c3ca 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1739,6 +1739,9 @@ static inline ssize_t call_write_iter(struct file *file, struct kiocb *kio, static inline int call_mmap(struct file *file, struct vm_area_struct *vma) { + if (unlikely(is_overlay_file(file))) + return overlay_mmap(file, vma); + return file->f_op->mmap(file, vma); } diff --git a/include/linux/overlay_util.h b/include/linux/overlay_util.h index 886be9003bf3..2cd66bc316cc 100644 --- a/include/linux/overlay_util.h +++ b/include/linux/overlay_util.h @@ -6,8 +6,10 @@ struct file; struct kiocb; struct iov_iter; +struct vm_area_struct; extern ssize_t overlay_read_iter(struct file *file, struct kiocb *kio, struct iov_iter *iter); +extern int overlay_mmap(struct file *file, struct vm_area_struct *vma); #endif /* _LINUX_OVERLAY_FS_H */ diff --git a/mm/mmap.c b/mm/mmap.c index 3714aa4e6f81..c43dfe1846d1 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1746,6 +1746,9 @@ unsigned long mmap_region(struct file *file, unsigned long addr, return error; } +/* + * Overlay needs special handling after copy-up + */ unsigned long unmapped_area(struct vm_unmapped_area_info *info) { /*